This application claims priority from Korean Patent Application No. 2000-30091, filed Jun. 1, 2000, the entirety of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a method for forming a capacitor of a semiconductor device, and in particular to an improved method for forming a capacitor of a semiconductor device which can increase a capacitance and prevent a leakage current at the same time.
2. Description of the Background Art
The capacitance of a capacitor used as a data storage unit in a semiconductor device is dependent upon the area of the electrode, the gap between the electrodes and the dielectric constant of a dielectric film inserted between the electrodes.
However, the semiconductor device has been highly integrated. Accordingly, the capacitor formation region of the semiconductor device has decreased, and thus the area of the electrode of the capacitor has also decreased, thereby reducing the capacitance of the capacitor.
Therefore, in a capacitor having a structure of metal film-dielectric film-metal film (MIM), an Ru film is deposited as a lower electrode, a TaON film having a high dielectric constant is deposited thereon, and a metal film is deposited on the dielectric film, thereby maximizing the capacitance of the TaON film capacitor.
FIGS. 1 and 2 are cross-sectional diagrams illustrating sequential steps of a conventional method for forming a capacitor of a semiconductor device.
As illustrated in FIG. 1, there is provided a semiconductor substrate (not shown) including a MOSFET (not shown). Here, a plug polysilicon film 5 and a metal barrier film 6 consisting of a Ti/TiN film are sequentially stacked on an interlayer insulation film 4 having a contact hole exposing one of the junction regions (not shown).
A cap oxide film 7 is deposited over the resultant structure in order to form a cylindrical capacitor.
Thereafter, the cap oxide film 7 is patterned to define a capacitor region and to expose the interlayer insulation film and the metal barrier film.
An Ru film 8 for a lower electrode is deposited over the patterned cap oxide film 7a. Here, the Ru film 8 is deposited as the lower electrode according to a general chemical vapor deposition (CVD).
As depicted in FIG. 2, a chemical mechanical polishing (CMP) process is carried out on the Ru film 8 for the lower electrode in order to expose the cap oxide film 7a. A cylindrical Ru film 8a is formed as the lower electrode, by removing the cap oxide film 7a. A TaON film 9 having a high dielectric constant is formed on the cylindrical Ru film 8a, and an upper electrode 10 is formed on the TaON film 9, thereby forming the capacitor of the semiconductor device.
However, the conventional method for forming the capacitor of the semiconductor device has the following disadvantages.
When the metal film is used as the lower electrode, the leakage current property can be improved according to the quality and step coverage of the lower electrode.
However, when the Ru film is deposited according to the CVD, the deposition rate of the Ru film is very slow on the oxide film. Moreover, the Ru film may be heterogeneously deposited according to the substructure, thereby reducing the step coverage and deteriorating the electric property, including a leakage current, of the TaON film capacitor.
Accordingly, the present invention provides a method for forming a capacitor of a semiconductor device which can improve an electric property, including a leakage current, of the capacitor by enhancing a step coverage of a lower electrode.
The present invention thus provides a method for forming a capacitor of a semiconductor device, including the steps of providing a semiconductor substrate where a plug polysilicon film and a metal barrier film consisting of Ti/TiN film have been sequentially filled in a contact hole of an interlayer insulation film; forming a cap oxide film on the semiconductor substrate; patterning the cap oxide film to define a capacitor region and to expose the interlayer insulation film and the metal barrier film; forming a nitride film over the whole substrate according to a plasma treatment using NH3 gas; forming an Ru film for a lower electrode on the nitride film; forming a cylindrical lower electrode, by performing a chemical mechanical polishing process on the Ru film and the nitride film, and removing the cap oxide film; forming an amorphous TaON film on the lower electrode; crystallizing the amorphous TaON film according to a thermal treatment; and forming a metal film for an upper electrode on the crystallized TaON film.
In addition, there is provided a method for forming capacitor of a semiconductor device, including the steps of providing a semiconductor substrate where a plug polysilicon film and a metal barrier film consisting of Ti/TiN film have been sequentially filled in a contact hole of an interlayer insulation film; forming a cap oxide film on the semiconductor substrate; patterning the cap oxide film to define a capacitor region and to expose the interlayer insulation film and the metal barrier film; forming a nitride film over the whole substrate according to a plasma treatment; forming an Ru film for a lower electrode on the nitride film; forming a lower electrode, by performing a chemical mechanical polishing process on the Ru film and the nitride film, and removing the cap oxide film; forming an amorphous TaON film on the lower electrode; crystallizing the amorphous TaON film according to an rapid thermal process (RTP); and forming a metal film for an upper electrode on the crystallized TaON film.